The MCS-48 microcontroller series was the first range of microcontroller from Intel and it was originally released in 1976. The first chips were the 8048, 8035 and 8748 and the 8048 is probably the most used chip of this family. The first chips were produced using NMOS and in the early 1980s they became available in CMOS. The chips were produced until the 1990tie but there are still a lot around these days.
The MCS-48 microcontroller series has a modified Harvard architecture, with internal or external program ROM and 64 to 256 bytes of internal (on-chip) RAM. The I/O is mapped into its own address space, separate from programs and data and that made it a perfect controller in f.i. keyboards and toys. The original IBM PC keyboard used an 8048 as its internal microcontroller.
Common chips that are still available today are:
| Device | Internal | Memory | Remarks |
| 8035 | none | 64 × 8 RAM | |
| 8038 | none | 64 × 8 RAM | |
| 8039 | none | 128 × 8 RAM | |
| 8040 | none | 256 × 8 RAM | |
| 8048 | 1K × 8 ROM | 64 × 8 RAM | 27× I/O ports |
| 8049 | 2K × 8 ROM | 128 × 8 RAM | 27× I/O ports |
| 8050 | 4K x 8 ROM | 256 × 8 RAM | |
| 8748 | 1K × 8 EPROM | 64 × 8 RAM | 4K program memory expandable, 2× 8-bit timers, 27× I/O ports |
| 8749 | 2K × 8 EPROM | 128 × 8 RAM | 2× 8-bit timers, 27× I/O ports |
Simple processor
The 8048 is a very simple (but powerful) processor, with only one A4 page of instructions. You can use the internal ROM and have a lot of I/O pins, but whem activating the EA pin, you can also map the ROM to outside and use a eeprom or eprom to hold the code.
Pinout 8048 microcontroller
Internal diagram of the 8048
Schematic 8048 with external Eprom
Intel_8048_Single_Board_Computer on GitHub
https://github.com/jim11662418/Intel_8048_Single_Board_Computer
A simple Intel 8048 Single Board Computer. The firmware was assembled with the Macro Assembler AS with full schematics and sourcecode of the project, even the sourcecode of a monitor programm. It is fun to play with such aq simple, but yet powerful, micrcontroller. There is a good open source assembler:
http://john.ccac.rwth-aachen.de:8000/as/